1. Field of the Invention
The present invention relates to an improved method and apparatus for applying solvent to tubing, other cylindrical objects or other flexible material. The present invention is especially applicable to high speed and mass production requirements where numerous pieces must be solvent bonded in rapid succession. Solvent bonding is the process of coating one piece of material with a chemical and then bringing the coated piece into contact with a second piece of material for the purpose of adhering the two together. The chemical serves to dissolve and melt a portion of the two adjoining surfaces such that the two surfaces are bonded together.
2. Description of the Prior Art
In almost all prior art embodiments, automatic solvent bonding is accomplished by applying the solvent or bonding chemical by means of an applicator such as a wick. The applicator is dipped into the solvent solution and then rubbed onto the surface of one of the two objects which are to be solvent bonded. In the case of tubing or other objects which are generally cylindrical in shape and have a hollow interior, the applicator is rubbed along the external surface at the location where the bond is desired. In the case of applying solvent to the internal portion of the hollow cylindrical object, an applicator somewhat in the shape of a pipe cleaner is inserted into the object and then rubbed around the interior surface at the location where the bond is to be formed.
In almost all prior art applications which involve manual solvent bonding, one of the pieces to be solvent bonded is manually dipped into a bath of solvent and then brought into contact with the other part to which it will be solvent bonded. This process is commonly known as dipping and dabbing. In another manual application which is known in the prior art, a syringe is filled with solvent and the surface to be solvent bonded is coated with solvent by squirting the solvent through a hypodermic needle located at one end of the syringe.
While the method and apparatus used in prior art applications is satisfactory for individual hand application or low speed automatic application of solvent for the purposes of solvent bonding where the applicator can be frequently cleaned, this method and apparatus is totally unsatisfactory in high speed mass production operations for several reasons. First, in a high speed mass production solvent bonding operation, the applicator is required to be coated with solvent and then apply the solvent to the desired surface very quickly and frequently. Due to the frequent dipping and the adhesive nature of the solvent, the applicator which is frequently in the form of a wick or pipe cleaner type structure becomes coated with dissolved material and must be cleaned or replaced. This is due to the fact that the solvent dissolves the material to which it is applied and then when this partially dissolved material is brought into contact with the second material, the partially dissolved material refuses or resolidifies thereby bonding the two components together. Since the applicator wick contacts this partially dissolved material, small amount of the partially dissolved material adheres to the wick. Therefore, the wick must be frequently cleaned or replaced. The cleaning and/or replacement of the applicator result in frequent machine down time. Second, the use of these applicators frequently results in an uneven coating of the surfaces since the quantity of solvent which adheres to the applicator after successive dippings cannot always be accurately controlled. The problem is especially severe when coating the internal surface of a narrow diameter tube or comparable object. Since the wick must be inserted into the tube, then possibly rotated and then removed, uneven coating frequently occurs. In addition, it is virtually impossible to prevent solvent from being placed on the edge of the interior surface. Therefore, in applications where it is desired not to have solvent on the edge of the interior surface, this result is almost impossible to achieve with the prior art embodiments.
Several different types of bonding and coating techniques are illustrated in the following issued patents:
1. U.S. Pat. No. 3,607,180 issued to Mars for Bonding With A Glass Frit Coating Applied By A Knurled Roller. PA1 2. U.S. Pat. No. 4,052,249 issued to Bruce for a Face Sealing Valve Applicator. PA1 3. U.S. Pat. No. 3,356,062 issued to Crowe for a Gravimetric Coating Control System. PA1 4. U.S. Pat. No. 2,617,456 issued to Winkel for a Lumber Gluing Machine. PA1 5. U.S. Pat. No. 2,396,946 issued to Grupe for a Method and Apparatus For Applying Thermoplastic Material To A Sheet Or Web. PA1 6. U.S. Pat. No. 2,199,228 issued to Obenshain et al for a Method Of And Apparatus For Coating Paper. PA1 7. U.S. Pat. No. 4,186,225 issued on a Method Of Coating The Interior Surfaces Of A Hollow Article. PA1 8. U.S. Pat. No. 3,697,313 issued to Stumphauzer et al on a Method Of Spraying Closed End Cans.
None of the above referenced patents disclose any apparatus or method for efficiently applying solvent on a rapid and mass production basis to an object. None are even remotely useful for applying solvent on a rapid and mass production basis to narrow diameter hollow cylindrical objects.